Question

我在EntityManager上得到null而我只是不知道为什么？

我的web.xml

<web-app id="WebApp_ID" version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

<display-name>Spring MVC Application</display-name>

<servlet>
    <servlet-name>mvc-dispatcher</servlet-name>
    <servlet-class>
                   org.springframework.web.servlet.DispatcherServlet
            </servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>

<servlet-mapping>
    <servlet-name>mvc-dispatcher</servlet-name>
    <url-pattern>/</url-pattern>
</servlet-mapping>

<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>/WEB-INF/mvc-dispatcher-servlet.xml</param-value>
</context-param>

<listener>
    <listener-class>
                  org.springframework.web.context.ContextLoaderListener
            </listener-class>
</listener>

我的mvc-dispatcher-servlet.xml

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
    http://www.springframework.org/schema/beans     
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
    http://www.springframework.org/schema/context 
    http://www.springframework.org/schema/context/spring-context-3.0.xsd">

<context:component-scan base-package="pl.wisecode.controller" />
<context:annotation-config />

<bean
    class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="prefix">
        <value>/WEB-INF/views/</value>
    </property>
    <property name="suffix">
        <value>.jsp</value>
    </property>
</bean>

<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" 
destroy-method="close">
    <!-- Connection properties -->
    <property name="driverClass" value="com.mysql.jdbc.Driver" />
    <property name="jdbcUrl" value="jdbc:mysql://localhost/wiseCode" />
    <property name="user" value="wiseCode" />
    <property name="password" value="asseronia1" />
    <!-- Pool properties -->
    <property name="minPoolSize" value="5" />
    <property name="maxPoolSize" value="20" />
    <property name="acquireIncrement" value="1" />
    <property name="maxStatements" value="50" />
    <property name="idleConnectionTestPeriod" value="3000" />
    <property name="loginTimeout" value="300" />
</bean>

<bean id="entityManagerFactory"
    class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="packagesToScan" value="pl.wisecode.model" />
    <property name="jpaVendorAdapter">
        <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
            <property name="showSql" value="true" />
            <property name="databasePlatform" value="org.hibernate.dialect.MySQLDialect" />
        </bean>
    </property>
    <property name="jpaProperties">
        <props>
            <prop key="hibernate.hbm2ddl.auto">update</prop>
        </props>
    </property>
</bean>
<bean
    class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" />
<bean
    class="org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor" />
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
    <property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>

我的DAO看起来像这样

public class UserDAO {

@PersistenceContext
private EntityManager entityManager;

@Transactional
public void dodajUuser(User user) {
    entityManager.merge(user);
}

}

我很多代码！ :(即时通讯新到春天，我只是不知道为什么我在entityManager上得到null，如果有人可以给我一些关于它的提示或告诉我在哪里我犯了错误我会非常感激！ PS。我没有任何persistence.xml是否有必要？如果它应该放在哪里呢？

使用Spring的EntityManager（空指针异常）

0 个答案: